The present invention relates to a mirror driving mechanism for a single lens reflex camera, especially to a pocket-type camera using a 16mm size film or 110 type film.
In most conventional single lens reflex cameras using film or other light sensitive materials which are of a size of 35mm and larger, a reflex mirror is supported within a mirror box by means of a supporting member having substantially the same size as that of the mirror. This supporting member is designed to rotate about an axis perpendicular to the optical axis of the objective lens of the camera. Examples of such systems are shown in U.S. Pat. Nos. 3,768,390 and 3,777,637, issued to Kobori and Kuramoto et al, respectively. In this respect, the rotations of the mirror and supporting member are controlled by a control mechanism which is mounted on the side wall and/or bottom wall of a mirror box.
Such an arrangement, however, is confronted by difficulties with a small size single lens reflex camera using a 16mm or 110 type film, i.e., when the reflex mirror is supported in the same manner as in the conventional type camera. In such a situation, the positional accuracy of the reflex mirror is hard to control because of the small size of the reflex mirror. Furthermore, the components of the mechanism to control the movement of the mirror should be made relatively small in size.
In general, the mirror control mechanism needs to accomplish three types of movements, i.e., (i) retaining the mirror in a viewing position, (ii) shifting the mirror from its viewing position to its picture-taking position in response to a shutter releasing operation, and (iii) returning the mirror back to its viewing position in response to the completion of a shutter closing operation. In addition, these movements of the control mechanism must be interrelated with a shutter-release-initiating mechanism, shutter driving mechanism and diaphragm mechanism, thus resulting in a complex arrangement. It is difficult, however, to fabricate such mechanisms with small size components so as to accommodate their sizes to such a small size mirror.
On the other hand, with the conventional type single lens reflex camera, the rear end of an objective lens is adapted to be positioned as close to a focal plane as possible, by allowing the tip of the reflex mirror to move in a substantially vertical direction. It is also difficult to adopt such a mirror control mechanism for a small size mirror.